SMART CONCRETE BRIDGE GIRDERS USING SHAPE CONCRETE BRIDGE GIRDERS USING SHAPE MEMORY ALLOYS . ......

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  • SMART CONCRETE BRIDGE GIRDERS

    USING SHAPE MEMORY ALLOYS

    Morgan State University The Pennsylvania State University

    University of Maryland University of Virginia

    Virginia Polytechnic Institute & State University West Virginia University

    The Pennsylvania State University The Thomas D. Larson Pennsylvania Transportation Institute

    Transportation Research Building University Park, PA 16802-4710 Phone: 814-865-1891 Fax: 814-863-3707

    www.mautc.psu.edu

  • FINAL REPORT

    SMART CONCRETE BRIDGE GIRDERS USING SHAPE MEMORY ALLOYS

    Osman E. Ozbulut, Ph.D. Assistant Professor University of Virginia

    Reginald F. Hamilton, Ph.D. Assistant Professor

    Pennsylvania State University

    August 15, 2015

  • 1

    DISCLAIMER

    The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. This document is disseminated under the sponsorship of the U.S. Department of Transportations University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof.

  • 2

    TABLE OF CONTENTS

    DISCLAIMER................................................................................................................... 1 TABLE OF CONTENTS ................................................................................................. 2 LIST OF FIGURES .......................................................................................................... 3 LIST OF TABLES ............................................................................................................ 5 ABSTRACT ....................................................................................................................... 6 INTRODUCTION............................................................................................................. 7 RESEARCH APPROACH ............................................................................................... 8 SHAPE MEMORY ALLOY MATERIALS CHARACTERIZATION..................... 10 GROUT CHARACTERIZATION ................................................................................ 36 PULL-OUT TESTS ........................................................................................................ 40 DISCUSSION OF RESULTS ........................................................................................ 42 CONCLUSIONS AND RECOMMENDATIONS ........................................................ 47 REFERENCES ................................................................................................................ 50

  • 3

    LIST OF FIGURES Figure 1. Self-post-tensioning process. ........................................................................................ 9 Figure 2. Phase transformation temperatures of SMAs. .............................................................. 10 Figure 3. Strain-temperature response of as-processed Ni47.7Ti43.5Nb8.8 (at%) material at constant

    stresses of 150 and 300 MPa. A Ni49.4Ti50.2 (at%) result loaded to 120 MPa is included for comparison. ........................................................................................................................... 11

    Figure 4. SEM images of the cast showing (a) an overview of the cellular arrangement, (b) the matrix encompassed by the eutectic in the region within the box in (a), and (c) is a 3D AFM image showing the varying surface topology. ....................................................................... 14

    Figure 5. SEM images showing (a) the deformation-processed microstructure with the Nb-rich particles oriented in the rolling direction, (b) a 3D AFM image of the smooth surface and (c) the cross-sectional view which is perpendicular to (a). ......................................................... 14

    Figure 6. High-magnification SEM images showing the Nb-rich particles in (a) cast and (b) deformation-processed microstructures. ................................................................................ 14

    Figure 7. Normalized heat flow vs temperature curves (i.e. thermo-grams) ................................ 15 Figure 8. Strain-temperature responses for thermal cycling under constant stress for (a) the cast

    alloy and (b) the deformation-processed alloy. The single and double arrows depict the slopes during cooling and heating respectively. The symbols are defined within the text. .. 16

    Figure 9. Characteristics parameters (a) forward TF and reverse TR transformation temperature intervals and (b) thermal hysteresis TH and recovery ratio for different levels of bias stress in Figure 8. ............................................................................................................................ 17

    Figure 10. Scanning electron micrographs showing white Nb-rich particles in an as-cast microstructure of Ni47.3Ti44.1Nb8.6(at%) material in (a) at 500 X magnification and (b) at 5000X magnification. (c) The microstructure of the as-processed material Ni47.7Ti43.5Nb8.8 (at%), investigated in this work, shown in the rolling direction at 500X magnification and (d) at 5000X magnification. (e) The cross-section view of the rolled strip material at 10000X magnification. In the text, (d) and (e) are contrasted with the solution annealed microstructure in Figure 11. .................................................................................................. 22

    Figure 11: SEM micrographs showing the white Nb-rich particles of the annealed material (900 C for 1hr) in the (a) rolling direction at 5000X and (b) cross-section at 10000X. These images are compared to the as-processed microstructure in Figure 10 (d) and (e). .............. 22

    Figure 12: Region of interest covering the speckle pattern on the specimen surface. The ROI dimensions used in the DIC analysis are included. The dashed ovals at the top and bottom mark that the ROI extends into the specimen grip section. Consequently, those regions remain unchanged during deformation in Figures 13-15. ..................................................... 23

    Figure 13. (a) The stress-strain response of as-processed material deformed at RT up to 8% average target strain and unloaded. (b) The strain-temperature response after unloading and during heating at null load. DIC strain contours are inset at selected points. The strain in the deformation fields is measured in the loading direction. In part (b), the scale has been adjusted to highlight the changes in strain contours during heating. ..................................... 25

    Figure 14: (a) The stress-strain response at 60 C, the material is deformed to 8% average strain and unloaded. (b) After unloading, the strain-temperature response during heating at null load. Inset images of strain contours are shown along selected points on both curves. The strain is in the loading direction. In part (b), the scale has been adjusted to highlight the changes in strain contours during heating. ............................................................................ 26

    Figure 15. The stress-strain response when annealed material is deformed at RT along with accompanying DIC strain fields at selected points. The strain in the deformation fields is calculated in the loading direction. ........................................................................................ 27

  • 4

    Figure 16. SEM images showing (a) the microstructure and (b) the micro-constituents in a cast Ni47.3Ti44.1Nb8.6 (at%) alloy and the microstructures of (c) the Ni47.7Ti43.5Nb8.8 (at%) alloy sheet (d) theNi44.6Ti42.8Nb12.6 (at%) alloy rod materials. ........................................................ 30

    Figure 17. The tensile stress-strain response of the NiTiNb alloys. ............................................. 31 Figure 18. (a) The stress-strain curves for pre-straining of sheet and rod; (b) the subsequent

    strain-temperature () response during shape memory recovery for sheet and rod materials. ............................................................................................................................... 33

    Figure 19. The tensile stress-strain curves for the sheet pulled to increasing pre-strain levels at room temperature................................................................................................................... 35

    Figure 20. The stress-temperature response during constrained heating and cooling of specimens that have been pre-strained to (a) 5.4%, (b) 10.1% and (c) 12.2%. The double arrows indicate heating, and the single arrows cooling. .................................................................... 36

    Figure 21. (a) Mixing grout with high shear Jiffler mixer. (b) Thermocouple attached to steel tendon. (c) Thermocouples on steel tendons and the data logger (d) Completed sample during temperature collection period ..................................................................................... 37

    Figure 22. Temperature measured in different commercially available grouts during curing. ... 39 Figure 23. (a) Pull-out test specimen and (b) test-set-up. ........................................................... 41 Figure 24. Bond stress-slip relationship for SMA bars at free end and loaded end for (a)

    Specimen 1 and (b) Specimen 2. ........................................................................................... 42 Figure 25. The variation of recovery ratio and recovery stress with pre-strain level for free and

    constrained recovery experiments ....................................................